Escalators and moving walkways are provided with combplate safety assemblies which are operable to shut the escalator down in the event that foreign objects become lodged between the treads and the exit combplate. These assemblies can be actuated by interrupting a light beam which passes beneath the combplate, such as disclosed in U.S. Pat. No. 4,800,998, granted Jan. 31, 1989 to R. E. Myrick; or by upward movement of the comb or the entire combplate, such as disclosed in the aforesaid copending application. Combplate safety systems have also been suggested which operate in response to bending or breaking of one or more of the comb teeth.
Safety systems of the character described will be included in new equipment, and are typically required by code to be incorporated into older equipment which has been in operation in the field for many years. Code changes can require that more sensitive systems be incorporated into existing and operating escalators and moving walkways.
Combplate safety systems that operate as a result of lifting the combplate, especially in older equipment, can be difficult to calibrate due to the fact that the weight of older combplates, and the ease of operation of their pivot mounts will vary widely. An example of this fact is apparent from recent code changes enacted with respect to escalators and moving walkways in the city of New York. The code changes require that the safety systems be actuated when the combplates are subjected to a lifting force of 30 lb. or more. Existing systems must be adapted to meet this new requirement. Given the fact that given combplates, even for common equipment, will not all weigh exactly the same, each will exhibit different resistance to upward movement due to variations in the manner in which they are mounted. These realities make adaptation of existing systems to meet the new code requirements very difficult. The data needed to accurately set or calibrate each system is: how far will the combplate be lifted from its normal or rest position when it is subjected to exactly 30 lbs. (or whatever other standard is established)? This piece of information is very difficult to empirically calculate for each different piece of equipment.